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<?php
/**
* Generate hash digests of file contents to help with cache invalidation.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
*/
class FileContentsHasher {
/** @var BagOStuff */
protected $cache;
/** @var FileContentsHasher */
private static $instance;
public function __construct() {
$this->cache = ObjectCache::getLocalServerInstance( 'hash' );
}
/**
* Get the singleton instance of this class.
*
* @return FileContentsHasher
*/
public static function singleton() {
if ( !self::$instance ) {
self::$instance = new self;
}
return self::$instance;
}
/**
* Get a hash of a file's contents, either by retrieving a previously-
* computed hash from the cache, or by computing a hash from the file.
*
* @private
* @param string $filePath Full path to the file.
* @param string $algo Name of selected hashing algorithm.
* @return string|bool Hash of file contents, or false if the file could not be read.
*/
public function getFileContentsHashInternal( $filePath, $algo = 'md4' ) {
$mtime = filemtime( $filePath );
if ( $mtime === false ) {
return false;
}
$cacheKey = $this->cache->makeGlobalKey( __CLASS__, $filePath, $mtime, $algo );
$hash = $this->cache->get( $cacheKey );
if ( $hash ) {
return $hash;
}
$contents = file_get_contents( $filePath );
if ( $contents === false ) {
return false;
}
$hash = hash( $algo, $contents );
$this->cache->set( $cacheKey, $hash, 60 * 60 * 24 ); // 24h
return $hash;
}
/**
* Get a hash of the combined contents of one or more files, either by
* retrieving a previously-computed hash from the cache, or by computing
* a hash from the files.
*
* @param string|string[] $filePaths One or more file paths.
* @param string $algo Name of selected hashing algorithm.
* @return string|bool Hash of files' contents, or false if no file could not be read.
*/
public static function getFileContentsHash( $filePaths, $algo = 'md4' ) {
$instance = self::singleton();
if ( !is_array( $filePaths ) ) {
$filePaths = (array)$filePaths;
}
Wikimedia\suppressWarnings();
if ( count( $filePaths ) === 1 ) {
$hash = $instance->getFileContentsHashInternal( $filePaths[0], $algo );
Wikimedia\restoreWarnings();
return $hash;
}
sort( $filePaths );
$hashes = array_map( function ( $filePath ) use ( $instance, $algo ) {
return $instance->getFileContentsHashInternal( $filePath, $algo ) ?: '';
}, $filePaths );
Wikimedia\restoreWarnings();
$hashes = implode( '', $hashes );
return $hashes ? hash( $algo, $hashes ) : false;
}
}
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